Smut

at flowering and grain-fill, instead of normal cobs, tassels or grain-heads you find swollen, distorted lumps (galls) where the grain should be. On maize they look like shiny, silver-grey boils or blisters — some as big as a fist — on the cob, tassel or stem.

those galls have a smooth silvery-white or grey skin that splits open to spill a mass of sooty black powder (the fungus spores) — like someone tipped soot or fine charcoal dust over the head. On sorghum, millet, wheat and barley you'll see whole grain-heads or single grains turned into black, dusty smutted grains instead of plump seed.

twisted, swollen tassels, cobs or seed-heads that never fill properly; and grain sites replaced by dark spore masses, sometimes held together by fine grey threads.

ordinary cob or head rot (that is soft, wet, and smells mouldy — smut galls are firm and dry, then powdery-black), bird or insect damage (that leaves torn or eaten grain, not a smooth swollen gall), or normal darkening of a ripe head. Smut's black dust is dry, fine and sooty, and it sits inside a swollen gall where good grain should have been.

from flowering through to harvest — the mid-season and late-season stages when tassels, cobs and grain-heads are forming and filling. This is when smut finally shows itself; there is nothing to see before then.

walk a large "W" shape so you cross all four corners and the middle, not just the row by the path. Make about 10 stops, and at each stop look closely at 10 plants.

the tassel (top), the cobs or grain-heads, the silks, and the stem and growing point — anywhere grain forms. You are hunting for swollen galls, silver-grey boils, or blackened grain replaced by sooty dust.

because there is no rescue spray, the threshold is a count of one. If you find even a single galled or smutted plant, act now — mark it and remove it before the gall bursts. Do not wait for it to spread; one burst gall throws out millions of spores that infect the soil and seed for next season.

Plant a smut-resistant or tolerant variety suited to your crop — this is your strongest single defence. Always sow certified clean seed, never grain saved from a field that had smut. Rotate — plant a different, non-cereal crop on that land for a season or two so the soil spores starve with no host to infect. And keep the crop unstressed at flowering: avoid moisture and nutrient shortage at heading, because dry, hungry plants are the ones smut hits hardest.

As soon as you spot a gall or smutted head, carefully cut it off — ideally with a bag or cloth over it so spores don't scatter — while it is still firm and unbroken. Burn or bury it deep; never leave it in the field and never put it in the compost or feed it to animals. Removing galls before the black dust escapes is the single act that stops next year's outbreak.

For seed- and seedling-infecting smuts, treat your seed before sowing with a systemic seed-treatment fungicide — systemic means it soaks into the young plant and protects it from inside; a seed dressing is powder or liquid coated onto the seed. Safety: wear gloves and cover your nose and mouth when coating seed; keep treated seed away from children, food, water and animals; never eat or grind treated seed or sell it as grain — it is poison, not food; and wash your hands well after handling it. To slow resistance, don't use the same product every season — rotate to a different chemical group when you can.

Once heads and cobs are smutted, no spray or effort will bring that grain back this season. Focus on stopping next year: rogue out and burn every galled plant you can before harvest, harvest the clean plants carefully so you don't spread dust onto good grain, and do not save any seed from this field. Next season, come back with a resistant variety, fresh certified seed and a rotation — that break in the cycle is what finally beats smut.